Clinical Case Challenge: Just another case of idiopathic IMHA?
A six-year-old, female spayed terrier mix originally presented to her referring veterinarian for a two-week history of lethargy and inappetence. Bloodwork revealed a normal chemistry and urinalysis, but a moderate-marked normocytic, normochromic anemia with a hematocrit of 18%, and reticulocyte count of 60 K/uL. A 4Dx SNAP test was faintly positive for Lyme. The dog’s owner also reported that she had started coughing and had been falling to the side.
She was brought to the Foster Hospital for Small Animals for further evaluation. On examination, the dog was moderately dehydrated. She had a phthisical left eye from a history of previous trauma, but her examination was otherwise unremarkable with no obvious neurologic deficits, and no melena appreciated.
Diagnostics at Foster Hospital revealed normal thoracic radiographs, and no abdominal masses or concerning findings on abdominal ultrasound. At this time, the dog’s anemia was similar with a hematocrit of 17% but had become regenerative with 115 K/uL reticulocytes. Rare spherocytes were found, but no agglutination was noted, and her bilirubin was still normal. Idiopathic IMHA was suspected, and the dog was given a packed red blood cell transfusion and started on dexamethasone at 0.3 mg/kg every 24 hours, cyclosporine at 7 mg/kg every 12 hours, doxycycline, and clopidogrel. Her PCV remained stable, so she was changed to oral prednisone at 1 mg/kg every 12 hours and discharged. Her PCV increased gradually and by two weeks after discharge was 30%, with 236 K/uL reticulocytes.
One month into treatment, the dog’s owners reported they suspected she had a mucoid stool with blood, and also that she had increased respiratory effort. On examination, the dog had mild enlargement of her right prescapular and left popliteal lymph nodes, and panted often in hospital, though her breathing was not noticeably labored. Her PCV had improved to 37% with only 131 K/uL reticulocytes, so her treatments were continued with a plan to reduce doses in two weeks. Prior to this appointment, the dog’s owners reported she had started chewing her feet and had seemed to develop an upper respiratory infection with nasal congestion and drainage. On examination, ulceration at her right lip commissure, persistent mild asymmetrical lymphadenopathy, and the following were noted:
The ulcerative foot lesions could suggest hepatocutaneous syndrome, though it is not usually associated with respiratory signs, or the nasal depigmentation and swelling noted in the patient. Bacterial and other secondary infections must always be considered in an animal receiving immunosuppressive medications. Other considerations could include an autoimmune process such as pemphigus foliaceus or systemic lupus erythematosus.
Biopsy of the affected footpads and nasal planum were recommended as a first step and agreed to by the dog’s owner. Other reasonable diagnostics would include thoracic radiographs, repeat serum chemistry, and potentially repeat abdominal ultrasound.
Histopathology of the affected tissues revealed severe, diffuse, granulomatous dermatitis and cellulitis with numerous intralesional algae consistent with Prototheca spp.
Prototheca organisms are ubiquitous but are more commonly found in warm, humid climates. Protothecosis is uncommon in dogs and rare in cats and usually presents with disseminated disease in dogs, though localized cutaneous disease can occur. Common sites of organism dissemination include the colon, eyes, brain and meninges, kidneys, and long bones.1 Fundic examination of the dog’s right eye revealed multifocal raised granulomas confirming disseminated disease:
The dog was rapidly tapered off her immunosuppressive medications, and began treatment with amphotericin B, itraconazole, and tetracycline. Now at six months, her condition remains improved on continued medications to treat the protothecosis, though cure is not usually possible in cases of disseminated disease.
It is unclear whether the dog’s original anemia presentation was triggered by underlying protothecosis, or if this developed rapidly when she became immunosuppressed. Non-regenerative anemia is uncommonly associated with Prototheca infection. Regardless, the dog’s case warns of the importance of a thorough search for underlying disease in cases of suspected idiopathic immune-mediated diseases, and close monitoring for complications of immunosuppressive therapy to allow timely interventions.
1. “Protothecosis.” Canine and Feline Infectious Diseases, by Jane E. Sykes, Elsevier/Saunders, 2014, pp. 679–685.